**2. Tetranychidae control Methods**

## **2.1 Chemical control**

Prior to world war II, spider mites were minor pests of agricultural crops. This changed rapidly after war, with the extensive use of chemical pesticides, such as DDT [5]. The chemical acaricides used to control Tetranychidae are characterized by a large variety of chemical structures and mode of actions which were reviewed by Attia et al. [6], Knowles [7] and Dekeyser [8]. A pesticide may have both direct and indirect effects on Tetranychidae. Some may kill immediately, while other pesticides take longer to kill. Others may affect mite performance by inhibiting movement and reducing searching ability or lowering oviposition rates. In addition some pesticides (such as carbaryl and DDT) have a stimulatory effect on spider mite reproduction when present in low concentrations. The stimulatory effect on mite reproduction is called hormoligosis. Hormoligosis is an ongoing problem, although it may not be recognized [9]. The chemical control of these mites has become increasingly difficult because of their short life cycle, abundant progeny and arrhenotokous reproduction system. The repeated use of pesticides can lead to the development of resistant population and also can disrupt the natural control of Tetranychidae. Because of its resistance to a large number of chemical compounds, the two-spotted spider mite, *Tetranychus urticae* Koch, is considered most resistant species nearly in all over the world [10].

#### **2.2 Cultural control**

Cultural control involve all agronomic practices that are intended to reduce pest population. Cultural practices include changing the time of planting and harvest to avoid or minimize pest damage. It is known that high humidity reduce the reproductive potential of Tetranychidae whose optimal environment is hot and dry air [11]. Proper management of temperature and humidity can be useful to reduce pests' populations in greenhouses. Managing fertilizer applications is another important cultural practice. Large quantities of nitrogen or deficiency of potassium can increase the amount of soluble nitrogen available in the plant so that cause population increase of *T. urticae* [11]. In our previous work on the effect of fertilizer Fosfalim-k application on cucumber and its effect on population growth of *T. urticae* we showed that its application in the recommended dose had a controlling effect [12].

Another example of cultural control is dust management. Dust management is important for control of Tetranychidae, especially in climates that crop irrigation occurs. Whether the dust makes the foliage more suitable for spider mites or interferes with the spider mites predators' performance is in controversy. The elimination of crop residues is another way that can destroy pests and prevent transferring to subsequent crops. Crop rotation and polycropping are other methods that can be used to manage pest population. It is not clear that polycropping is useful in phytophagous mites control but if natural enemies are retained in the crops it could be helpful [9]. In our previous work we showed that the intercropping of sunflower and soybean increased natural enemies compared with monocultures [13].
